JavaFX Scene Builder
In 2012 I did the early designs for the JavaFX designer tool that went on to become SceneBuilder. From 2012 to 2014 I worked closely with the amazing SceneBuilder team and we produced a really nice usable tool for designing UI for JavaFX. After several years of Oracle shipping SceneBuilder it was open sourced. The project is now pure open source and Gluon are kindly doing builds.
Over a couple years, the tool had a few different design directions and themes. Starting as more of a rich media animation tool like Adobe Flash, later becoming an enterprise application builder.
At one point we were thinking of having the application be a cloud service. I did some initial designs but it was never taken any further.